1. Field of the invention
The present invention relates to charging control for a user service running on a communication connection. In particular, the present invention relates to a mechanism for correcting charging control information used for the charging control.
2. Related Prior Art
In the last years, an increasing extension of communication networks, e.g. of wire based communication networks, such as the Integrated Services Digital Network (ISDN), or wireless communication networks, such as the cdma2000 (code division multiple access) system, cellular 3rd generation (3G) communication networks like the Universal Mobile Telecommunications System (UMTS), cellular 2nd generation (2G) communication networks like the Global System for Mobile communications (GSM), the General Packet Radio System (GPRS), the Enhanced Data Rates for Global Evolutions (EDGE), or other wireless communication system, such as the Wireless Local Area Network (WLAN) or Worldwide Interoperability for Microwave Access (WiMax), took place all over the world. Various organizations, such as the 3rd Generation Partnership Project (3GPP), Telecoms & Internet converged Services & Protocols for Advanced Networks (TISPAN), the International Telecommunication Union (ITU), 3rd Generation Partnership Project 2 (3GPP2), Internet Engineering Task Force (IETF), the IEEE (Institute of Electrical and Electronics Engineers), the WiMAX Forum and the like are working on standards for telecommunication network and access environments.
In order to bill services used by a subscriber or user, a policy and charging control (PCC) can be implemented in communication systems. Such PCC architectures are specified in several specifications, for example by 3GPP, as known by those skilled in the art. PCC enables a service specific charging and policing of services. It may encompass different high level functions for IP Connectivity Access Networks (IP-CAN, e.g. GPRS, I-WLAN, Fixed Broadband, etc.), such as Flow Based Charging, including charging control and online credit control, and policy control (e.g. gating control, Quality of Service (QoS) control, etc.).
In a PCC network architecture, such as one based on 3GPP specifications, for example, a policy and charging rules function (PCRF) provides a policy and charging enforcement function (PCEF) with so-called policy and charging control rules (PCC rules). Media sent or received by a user equipment (UE) are transferred via the IP-CAN and through the PCEF which controls the related IP CAN connections. For charging purposes, the PCEF also collects information which is forwarded as charging records to, for example, an offline charging system (OFCS), and/or manages credits received from an online charging subsystem (OCS). The PCRF may derive PCC rules from information about ongoing services that is provisioned by so-called application function(s) (AF) towards the PCRF. In addition, the PCRF may provide PCC rules not related to any services provisioned by an AF.
It is to be noted that in case services are provisioned by an IP Multimedia subsystem (IMS), a so-called Proxy Call Session Control Function (P-CSCF) may act as an AF.
It is possible that different charging rates are applied. For example, applicable charging rates may differ between AF controlled services and other services. For instance, services provided by the IMS may be set free of charge in the PCC, for example since charging may be performed by non-PCC related entities. On the other hand, non-IMS related services may be charged by PCC.
When the UE requests a set up or modification of an IP CAN connection, the PCEF informs the PCRF about this request. Furthermore, the PCEF may request PCC rules. However, there might be situations where the PCRF is not able at this point in time to answer in a way that all possible usages of the IP-CAN session are authorized, i.e. to decide whether the UE request belongs to a service which is AF controlled or not. This may occur, for example, when the related AF has not yet provisioned the corresponding service information.
For illustrating such a situation, the following example may be considered. For instance, there may be a problem in case of an UE-initiated bearer setup at the terminating side of an IMS-controlled call setup, if resources at the originating side are already available. Here, the UE may set up a bearer before an SDP answer is sent, while service information may be provisioned from the P-CSCF to the PCRF only when an SDP answer is available in SIP signalling. Thus, a wrong charging of services may result during the time until service information becomes available from the AF.
However, according to the signalling protocol applied on, for example, a Gx interface between the PCRF and the PCEF, updates to PCC rules apply only from the point in the time onwards when they are provisioned to the PORE. Such PCC rule updates are typically used to support changes in the charging that take affect at this point in time, for example in case the rate for a service depends on the time of day when the service is used.
Consequently, a charging related PCC rule update is only relevant from the point in time onwards. Therefore, it would not be possible to charge a service correctly before the time the relevant service information are available, i.e., for example, before the AF provides the service information and the PCRF updates the PCC rules.
In other words, a policy and charging control unit, such as a PCRF, is not able to trigger the charging systems to correct charging control information relating to a point in time prior to an update of a PCC rule, i.e. for the period in time between the PCC rule activation and the charging related PCC rule update.
There are several approaches conceivable for dealing with such a situation. For example, one possible solution to avoid overcharging while the type of service is still unknown is allowing a service free of charge for a timer-supervised period. However, a timer in the order of, for example, up to 30 seconds may be required to cope with call flows encountered in IMS, and a considerable loss of income and fraud potential may render this solution inacceptable for an operator.
It has also been suggested to block service flows at the PCEF for the timer-supervised period to avoid fraud. However, this may severely impact the user experience in particular for non-IMS services such as Web browsing.
Another solution may be a modification of P-CSCF procedures to provide service information derived from the SDP offer. However, this service information will not contain all IP address and port information and may thus not be sufficient to “bind” it with traffic flow templates (TFTs) received for the IP CAN. Thus, the PCRF may not be able to unambiguously identify services even with this amendment. Further, UEs may set up or modify bearers for a service prior to sending any related SIP signalling and SDP. This behaviour can be expected for instance from a 3GPP2 UE starting a call setup. For such a scenario, such an approach would also not provide a proper solution.